1. Field of the Disclosure
The present disclosure relates to field of mobile terminals, and more particularly, to a charging circuit and a mobile terminal.
2. Description of the Related Art
Since mobile terminals are widely popular, the suppliers pay more attention on battery charging of the mobile terminals.
FIG. 1 is a circuit diagram of a charging circuit used in a mobile terminal. The charging circuit, called a BUCK circuit, includes a metal oxide semiconductor (MOS) transistor, a control circuit, a diode, an inductor, and a battery. When the mobile terminal is charged, the control circuit controls the MOS transistor to alternatively turn on/off, so as to produce alternating current (AC) square wave signal. The square wave alternating current from the MOS transistor is first regulated by the inductor and then flows through the battery.
In conventional technology, there is a risk of the breakdown of the MOS transistor, which can result in that an overcurrent flows through the inductor, and the battery. Furthermore, the battery may be improperly charged to exceed the threshold voltage thereof, thereby causing a failure of the battery.
The failure of the MOS transistor may arise from the following aspects:
1. Improper operation of the MOS transistor caused by voltage applied across two terminals of the MOS transistor in excess of the threshold voltage, electrostatic breakdown, or surge current impact;
2. Poor quality of the MOS transistor or defects in manufacturing;
3. Other defects.
To solve the above-mentioned problem arised from the failure of the MOS transistor and to enhance the reliability of the charging circuit, the conventional solution is likely to increase an on-resistance RDS(ON) of the MOS transistor so as to improve a breakdown threshold voltage of the MOS transistor. However, high on-resistance RDS(ON) may cause heat accumulation of the MOS transistor due to current heating effect and a low power transmission efficiency of the charging circuit.